1. Field of the Invention
The present invention relates to tube coupling system for a pressurised fluid system comprising a coupling body for receiving a tube of a pressurised fluid system, a leakage sealing means for preventing fluid from the pressurised fluid system to enter the coupling body, a gripping means for gripping the outer surface of the tube received in the coupling body, and an environment sealing means for preventing intrusion from outside of the coupling body.
2. Description of the Related Art
In many applications tubes must be connected with each other or with other components in such a way that leakage is prevented and unintentional release of the tube is precluded. This is particularly important in systems where malfunction and failure of the tube coupling can be hazardous and lead to serious damages, for instance in a braking system of a vehicle. A typical tube connector for such a purpose can be found in WO 2006/112726 A1.
The most common failure in form of leakage and unintentional release is due to an incorrect assembly when the tube is connected to a coupling system. The case that the tube is not sufficiently inserted into a coupling system is an example of such an incorrect assembly. Especially when the insertion force is high due to tight gripping or sealing means that are used in high-pressure systems, the engagement of the tube with a final stop portion may not be evident to a user during manual assembly. In addition, if the end of the tube is not cut at right angle, e.g. because it was manually shortened before assembly, the point of sufficient insertion can be vague.
Therefore, some feedback is needed indicating the assembler when the tube is sufficiently and correctly inserted in a coupling body.
It is known to provide visual markings on the outer surface of the tube giving the assembler a visual indication on when a predetermined insertion depth has been reached. This can for example be a line that needs to be covered by the coupling body when the tube is sufficiently inserted into the coupling system. However, this solution is disadvantageous as the tube cannot be shortened to an appropriate length without losing the visual markings at one or both ends. Furthermore, there is an uncertainty about the positioning of the marking and the ability to judge whether the visual markings indicate full insertion or not.
Other common solutions provide the user with a recognizable push-in feeling that indicates when the tube is in correct position. This requires that the user is able to make a distinction in the feeling which is for example difficult when using, a tool for assembly. Moreover, a recognisable push-in feeling is a highly subjective measure which various users might experience differently.
A tube coupling system according to the preamble of claim 1 is known from WO 2006/112726 A1. However, the problem of providing the assembler with a feedback signal when the tube is sufficiently and correctly inserted is not addressed therein.
WO 2006/037962 A1 discloses a tube coupling and addresses the feedback problem by providing an audible indication of the fully-inserted position of the tube. The coupling system disclosed therein comprises a tube support member on which a tube is slid on to. During insertion of the tube into the coupling the tube pushes in the tube support member which is therefore urged to slide deeper into the coupling body. A groove and tongue configuration between the outer surface of the tube support member and the inner surface of the coupling body provides an audible click signal notifying the user that the tube with the tube support member has reached a fully-inserted position.
The solution described in WO 2006/037962 A1 has the disadvantage that the audible click signal only notifies the user indirectly, namely that tube support member has reached a fully-inserted position rather than the tube being fully inserted into the coupling. So, there is no information given whether the tube is really fully inserted in the tube support member. The risk of leakage and unintentional release due to an incorrect assembly of the tube into the tube support member therefore still remains. In addition, there is no information given whether the tube remains in the correct fully-inserted position during normal use of the tube coupling system. Furthermore, the push-in force during insertion of the tube is significantly increased by the resistance that the groove and tongue configuration poses to produce an audible click signal. This resistance must be relatively large, because a premature click signal before the tube has reached a final stop portion of the tube support member would be detrimental. This resistance force adds up to the friction caused by gripping or sealing means yielding an uncomfortably high total push-in force. Such a required high total push-in force in turn can easily lead to a high frictional force between the tube and the tube support member when the tube is applied in a slightly tilted way, for example. If this frictional force exceeds the click resistance, a detrimental premature click signal is triggered before the tube is fully inserted into the tube support member.
The object of the present invention is to overcome the disadvantages of the prior art and to provide a tube coupling system that really assures a user of the tube being sufficiently and correctly inserted into the coupling after assembly and during normal use. Furthermore, a continuous check of the leak tightness is desirable.